1. Field of the Invention
This invention relates to thermally responsive photographic processing apparatus and, more particularly, to processing apparatus including temperature responsive fluid distribution control means for use with self-processable film units.
2. Description of the Prior Art
Photographic processing apparatus for use with self-processable type film units are well known and generally comprise a pair of elongated juxtaposed pressure applying members between which an exposed film unit is advanced to initiate a photographic diffusion transfer process for developing and forming a visible image in the film unit.Such film units, as for example those described in considerable detail in U.S. Pat. Nos. 2,543,181; 3,415,644; and 3,594,165, normally contain all the photographic components necessary for the diffusion transfer process. Physically, these film units typically comprise a pair of superposed sheet elements which serve to support layers of photochemical substances that comprise photosensitive and image-receiving layers; and, as well, include as an integral part a rupturable container of viscous processing fluid positioned adjacent a leading edge of the film unit and adapted to have the processing fluid released between the sheet elements to initiate the diffusion transfer process. Subsequent to exposure, the film unit is advanced, leading edge first, through the pressure applying members which serve first to rupture the container to release the processing fluid and then to cause the released mass of processing fluid to flow between the sheet elements, opposite to their direction of travel, so that the processing fluid is progressively deposited between the sheet elements as a thin layer coextensive with the exposure area of the film unit as the film unit is advanced between the pressure applying members.
For optimum photographic image quality with film units utilizing this type of process, it is generally recognized that the thickness of the processing fluid layer must be maintained at a substantially constant predetermined thickness value which is uniform over the photoexposed area of the film unit. However, there are a number of factors which may affect the thickness and uniformity of the processing fluid layer. Among these is the viscosity of the fluid itself.
Changes in the viscosity of the processing fluid come about because its nature and composition are such that its viscosity, in general, may vary with changes in temperature. Moreover, because photographic systems such as cameras and the like employing such film units and processing apparatus are used both indoors and outdoors over a range of temperatures, the viscosity of the processing fluid changes with the ambient operating temperature of the system. This situation presents a problem in maintaining the thickness and uniformity of the fluid layer constant over the temperature operating range of the photographic system.
There are a number of prior art disclosures which recognize this problem and provide apparatus and structure for compensating for changes in the thickness and uniformity of the processing fluid layer caused by temperature induced changes in the processing fluid's viscosity. For example, U.S. Pat. No. 3,589,262 issued to Richard J. Chen on June 29, 1971 and entitled "PHOTOGRAPHIC PROCESSING APPARATUS" and U.S. Pat. No. 3,732,099 also issued to Richard J. Chen on June 21, 1968 and entitled "TEMPERATURE SENSITIVE PRESSURE-APPLYING MEMBERS FOR A PHOTOGRAPHIC PROCESSING LIQUID" collectively disclose apparatus and processes which include "means for automatically sensing the ambient temperature and responding by varying the compressive pressure exerted by rolls (pressure applying members) on the film unit in inverse relation to the temperature so as to maintain constant a relationship between liquid viscosity and compressive pressure that will insure spreading of the processing liquid in a layer of predetermined depth even though the temperature and viscosity may vary." And in U.S. Pat. No. 3,604,329 issued to Edwin H. Land on Sept. 14, 1971 and entitled "PHOTOGRAPHIC APPARATUS AND PROCESS FOR CONTROLLING THE DEVELOPMENT OF INDIVIDUAL FILM UNITS AS A FUNCTION OF TEMPERATURE" the disclosure provides "means for automatically sensing the ambient temperature and varying the rate of rotation of the rolls (pressure applying members) in accordance with temperature so as to maintain constant a relationship between liquid viscosity and speed of movement of the film unit that will insure spreading of the processing liquid in a layer of predetermined depth even though the temperature and viscosity may vary." Also, this disclosure suggests that it may be advisable to vary the pressure exerted by the rolls on the film unit in combination with varying the roller speed. While the foregoing patents disclose structure for solving the problem, they utilize a complex structure and mechanism for varying the actual pressure exerted by the rolls to a film unit.
A number of other prior art patents do disclose means for applying a second pressure for purposes of controlling the flow of the processing fluid as it is spread in the film unit after exposure. Patents in this category include: U.S. Pat. No. 2,991,703 issued to V. K. Eloranta on Aug. 29, 1958 and entitled "PHOTOGRAPHIC APPARATUS"; U.S. Pat. No. 3,777,647 issued to Edwin H. Land on Dec. 11, 1973 and entitled "PHOTOGRAPHIC APPARATUS AND METHOD FOR TREATING PHOTOGRAPHIC MATERIALS WITH A LIQUID"; U.S. Pat. No. 3,241,468 issued to O. E. Wolff on Mar. 22, 1966 and entitled "PHOTOGRAPHIC APPARATUS"; U.S. Pat. No. 3,820,137 issued to John J. Driscoll on June 25, 1974 and entitled "PHOTOGRAPHIC APPARATUS"; and U.S. Pat. No. 3,779,770 issued to William W. Alston, John J. Driscoll and Richard R. Wareham on Dec. 18, 1973 and entitled "PHOTOGRAPHIC FILM ASSEMBLAGE FOR A DIFFUSION TRANSFER FILM". However, none of these disclosures deal with the problem of compensating for temperature related viscosity changes.
Therefore, it is a primary object of the invention to provide a simplified photographic processing apparatus for use with self-processable type film units to compensate for variations in the thickness of a processing fluid layer caused by temperature related changes in the fluid's viscosity as the fluid is spread in a thin layer in the film unit.
Another object of this invention is to provide a simplified photographic processing apparatus for use with self-processable type film units having means for applying a second pressure to the film unit as a viscous fluid processing fluid is spread in a thin layer between a pair of sheet elements of the film unit to oppose the flow of the processing fluid relative to the sheet elements to compensate for temperature related viscosity changes in the fluid so as to maintain the thickness of the processing fluid layer substantially constant over a predetermined range of operating temperatures of the apparatus.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.